The kidney bean sign (more commonly called the coffee bean sign; also bent inner tube sign) is a radiologic sign observed on abdominal radiographs that indicates the presence of a sigmoid volvulus, a form of bowel obstruction. It is seen as an area of hyperlucency resembling a coffee bean.[1] The opposed walls of adjacent bowel loops form the central cleft while the two sides of the bean represent gas‐filled segments of dilated bowel that form an inverted U‐shape.[2] Air-fluid levels may also be seen in the segments of dilated bowel.[1]
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